Efficient scrubbing of mirrored memory

ABSTRACT

A method comprising of allocating a main memory partition and a mirrored memory partition, a mirrored copy of the main memory partition, of a mirrored memory system for scrubbing. The method also comprises of dividing the main memory partition into a first main portion and a second main portion and dividing the mirrored memory partition into a first mirrored portion and a second mirrored portion. The method determines a full scrub cycle that only scrubs a portion of the main memory channel and a portion of the mirrored memory partition, the full scrub cycle including scrubbing a main scrub portion, one of the first and the second main portions, and a mirrored scrub portion, one of the first and the second mirrored portions. The method initiates the full scrub cycle which includes a combination of memory portions, equivalent to a memory address range of the main memory partition.

BACKGROUND OF THE INVENTION

The present invention relates to computer systems, and morespecifically, to mirrored memory scrubbing of computer memory errors.

Computer memory chips are susceptible to natural background radiationsuch as cosmic rays and alpha particles. For example, radioactiveelements in a computer chip's material decay and release alpha particlesinto the chip. Radiation such as this occasionally causesinconsistencies within a system's memory which result in errors. Sucherrors are often referred to as soft errors. This natural radiation cancause a memory cell to change state to a different value, while notaltering the physical structure of the computer chip. Soft errors rangefrom a variation in an instruction within a program, to a modificationin a single data value. The probability of a soft error occurring isrelatively small. However, with the large amount of memory included inmodern computer systems, the rate of occurrence increases significantly.

Memory scrubbing is a process used to correct errors of memory locationsby inspecting and correcting errors using error-correcting code (ECC),as well as replacing the corrected data back in its original location.This process is done periodically as a background operation of a system.

A memory controller scans through a system's memory and determines wheresoft errors occur. ECC is generally implemented to correct detected softmemory errors, then replaces the detected errors with corrected data atthe appropriate location. Memory scrubbing is often classified as areliability, availability, and serviceability (RAS) feature as itgenerally increases reliability of a system's memory.

The memory scrubbing process is done periodically, in the background ofa system, rather than constantly. Performing memory scrubbing generallyrequires additional system power to check for and correct errors, aswell as requires additional logic in the memory controller to manage thereading of the memory.

A mirrored memory system consists of a division of memory into twomemory channels, sometimes referred to as memory partitions. Data storedin a main memory channel is duplicated in a mirrored memory channel. Ifa soft error occurs in the main memory channel, the mirrored memorychannel can be used to access the correct data or instruction, and ECCis applied to correct errors and reflect identical information.

For mirrored memory systems, the main memory and mirrored memory areidentical, other than for unpredictable soft errors, therefore, errorsfound in one memory channel can be corrected using the correspondingmemory location of the other memory channel. The main memory andmirrored memory are scrubbed concurrently during the memory scrubbingprocess.

SUMMARY

Embodiments of the present invention disclose a method, a computerprogram product, and a system for scrubbing memory. The method comprisesof allocating a main memory partition of a mirrored memory system and amirrored memory partition of the mirrored memory system for scrubbing,the mirrored memory partition being a mirrored copy of the main memorypartition. The method also comprises of dividing the main memorypartition into a first main portion and a second main portion anddividing the mirrored memory partition into a first mirrored portion anda second mirrored portion. The method determines a full scrub cycle thatonly scrubs a portion of the main memory channel and a portion of themirrored memory partition, the full scrub cycle including scrubbing amain scrub portion and a mirrored scrub portion, the main scrub portionbeing one of the first and the second main portions and the mirroredscrub portion being one of the first and the second mirrored portions.The method initiates the full scrub cycle where the full scrub cycleincludes a combination of memory portions, the combination beingequivalent to a memory address range of the main memory partition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a distributed dataprocessing environment, in accordance with one embodiment of the presentinvention.

FIG. 2 is a block diagram illustrating mirrored memory channels of acomputer server operating within the distributed data processingenvironment of FIG. 1, in accordance with an embodiment of the presentinvention.

FIG. 3 illustrates operational steps of a scrub controller program,included within a memory controller of the computer server, within thedistributed data processing environment of FIG. 1, in accordance with anembodiment of the present invention.

FIG. 4 illustrates additional operational steps of the scrub controllerprogram, included within the memory controller of the computer server,within the distributed data processing environment of FIG. 1, inaccordance with an embodiment of the present invention.

FIG. 5 depicts a block diagram of components of a computing system,which includes a computing device capable of operating the scrubcontroller program of FIG. 3, in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

Embodiments of the present invention recognize that memory scrubbingoperations consume processor time and operational power to check memoryconsistency and perform any necessary corrections. Although memory scruboperations provide benefits in terms of increasing reliability,availability, and serviceability (RAS), such operations have drawbacks,such as, (i) increased power consumption due to parsing a large amountof data, and (ii) the additional logic that is required in the memorycontroller to manage the read operation by inserting cycles in thescheduler queue.

Embodiments of the present invention provide a computer-implementedmethod for memory scrubbing that omits scrubbing of redundant portionsof a memory. Instead of scrubbing the entirety of both the main memorychannel and the mirrored memory, only portions of the memory that areselected are scrubbed, reducing the overall power usage. Generally,mirrored memory systems include scrubbing of both the main and mirroredmemories in their entirety. If, for example, it takes 24 hours and 10Watts (W) of power to scrub the entire address range of one channel ofmemory, it would take 24 hours and 20 W to scrub both channels of memoryin a mirrored memory system when done concurrently.

Embodiments of the present invention propose dividing the address rangesof the duplicate memory channels of mirrored memory systems, andscrubbing alternate halves of each memory channel, effectively scrubbingan equivalent of one memory channel. Referring to the previous time andpower examples for a standard scrub of a mirrored memory system,scrubbing half the address range of the main memory channel would take12 hours and 5 W. When done concurrently with half the total memoryaddress range of the mirrored memory channel, it would take 12 hours and10 W. Therefore, embodiments of the present invention provide a netbenefit of 50% of both the time and power consumption needed to scrubthe equivalent of the total memory address range, using the duplicationattribute of a standard mirrored memory system.

Further, embodiments of the present invention provide a method ofscrubbing half of the entire memory address range while ensuring that anequivalence of the contents of the entire memory address range completescrubbing for each scrubbing cycle. Embodiments of the present inventionidentify and correct soft errors by scrubbing one half of each of theidentical memory channels and avoid scrubbing redundant memory portions.

The present invention will now be described in detail with reference tothe Figures. FIG. 1 is a functional block diagram illustrating adistributed data processing environment, generally designated 100, inaccordance with one embodiment of the present invention. FIG. 1 providesonly an illustration of one implementation and does not imply anylimitations with regard to the environments in which differentembodiments may be implemented. Many modifications to the depictedenvironment may be made by those skilled in the art without departingfrom the scope of the invention as recited by the claims.

Distributed data processing environment 100 includes computer server110, which further includes memory 112 and memory controller 130; andcomputer server 120, which further includes memory 122 and memorycontroller 132; all of which are interconnected via network 140. Memory112 contains main memory channel 114 and mirrored memory channel 116.Memory 122 contains main memory channel 124 and mirrored memory channel126. Memory controller 130 of server 110 is depicted as including scrubcontroller program 300.

Network 140 can be, for example, a telecommunications network, a localarea network (LAN), a wide area network (WAN), such as the Internet, ora combination of the three, and can include wired, wireless, or fiberoptic connections. Network 140 can include one or more wired and/orwireless networks that are capable of receiving and transmitting data,voice, and/or video signals, including multimedia signals that includevoice, data, and video information. In general, network 140 can be anycombination of connections and protocols that will supportcommunications between computer server 110, computer server 120, andother computing devices (not shown) within distributed data processingenvironment 100.

In some embodiments of the present invention, computer server 110 andcomputer server 120 can either or both be a standalone computing device,a management server, a web server, a mobile computing device, or anyother electronic device or computing system capable of receiving,sending, and processing data. In other embodiments, either or bothcomputer server 110 and computer server 120 can represent a servercomputing system utilizing multiple computers as a server system, suchas in a cloud computing environment. In another embodiment, computerserver 110 and computer server 120 can either or both be a laptopcomputer, a tablet computer, a netbook computer, a personal computer(PC), a desktop computer, a personal digital assistant (PDA), a smartphone, or any other programmable electronic device capable ofcommunicating with each other and other computing devices (not shown)within distributed data processing environment 100 via network 140. Inanother embodiment, either or both computer server 110 and computerserver 120 represents a computing system utilizing clustered computersand components (e.g., database server computers, application servercomputers, etc.) that act as a single pool of seamless resources whenaccessed within distributed data processing environment 100. Computerserver 110 includes memory 112 and memory controller 130, which areinterconnected by communication bus 118. Computer server 120 includesmemory 122 and memory controller 132, which are interconnected bycommunication bus 128. Computer server 110 and computer server 120 mayinclude internal and external hardware components, as depicted anddescribed in further detail with respect to FIG. 5.

Memory 112 and memory 122 may comprise a random-access semiconductormemory, storage device, or volatile storage medium for storing orencoding data and programs. In some embodiments of the presentinvention, memory 112 and memory 122 represent the entire memory ofcomputer server 110 and computer server 120, respectively, and may alsoinclude the memory of other computing devices (not shown) withindistributed data processing environment 100 via network 140. Memory 112and memory 122 are depicted as a single monolithic entity, but in otherembodiments of the present invention, memory 112 and memory 122 are amore complex arrangement, such as a hierarchy of caches, or other memorytypes. For example, memory may exist in multiple levels of caches, andthese caches may be further divided by function, so that one cache holdsinstructions while another holds non-instruction data, which is used bythe processor or processors. Memory may be further distributed andassociated with different CPUs or sets of CPUs, as is known in any ofvarious so-called non-uniform memory access (NUMA) computerarchitectures.

Memory 112 is partitioned into main memory channel 114 and mirroredmemory channel 116, in which mirrored memory channel 116 is a redundantcopy of main memory channel 114. For example, the content of themirrored memory partition, such as mirrored memory channel 116, is acopy of the content of the main memory partition, such as main memorychannel 114. In some embodiments of the present invention, memory 112 isfully mirrored, such that main memory channel 114 and mirrored memorychannel 116 include the full memory address range of memory 112 and areequivalent in size. In other embodiments of the present invention, mainmemory channel 114 and mirrored memory channel 116 may not be equivalentin capacity. It is noted that memory channel 114 and mirrored memorychannel 116 are intended to be duplicates of each other for redundancypurposes. In some instances, a memory address of a memory channel, suchas main memory channel 114, may be affected by a soft error at aparticular memory address location. The soft error may create a changein the contents of one memory channel, such as main memory channel 114,causing it to be different at a particular memory address from thecorresponding memory channel address, such as mirrored memory channel116.

Similar to memory 112, memory 122 is partitioned into main memorychannel 124 and mirrored memory channel 126, in which mirrored memorychannel 126 is a redundant copy of main memory channel 124. In someembodiments of the present invention, memory 122 is fully mirrored, suchthat main memory channel 124 and mirrored memory channel 126 include thefull memory address range of memory 122 and are equivalent in size. Inother embodiments of the present invention, main memory channel 114 andmirrored memory channel 116 are equivalent in capacity.

Memory controller 130 reads and/or writes data in memory 112 viacommunication bus 118. It is noted that memory controller 130 may readand/or write data in memory 112 via alternative mediums not depicted inFIG. 1. Memory controller 132 reads and/or writes data in memory 122 viacommunication bus 128. It is noted that memory controller 132 may readand/or write data in memory 122 via alternative mediums not depicted inFIG. 1. Memory controller 130 and memory controller 132 may perform aplethora of functions during the operation of the computing process,including scrub operations. Memory controller 130 and memory controller132 may initiate memory control operations based on instructions fromcomputer server 110 and computer server 120, respectively, such asprograms designed to perform memory control procedures, and/or userinput. Memory controller 130 is depicted as including scrub controllerprogram 300.

Scrub controller program 300 performs operations to improve efficiencyand reduce power consumption during scrub operations on both main memorychannel 114 and mirrored memory channel 116. In some embodiments of thepresent invention, scrub controller program 300 equally divides theaddress range of main memory channel 114 and mirrored memory channel116. Dividing the address range of main memory channel 114 and mirroredmemory channel 116 enables scrub controller program 300 to efficientlyand effectively scrub a first half of main memory channel 114 and asecond half of mirrored memory channel 116, reducing the time and energyconsumption to complete scrubbing operations of effectively a fullmemory address range. In some embodiments of the present invention,scrub controller program 300, residing on computer server 110, performsscrub operations on memory external to computer server 110, such as mainmemory channel 124 and mirrored memory channel 126 of memory 122residing on computer server 120. Scrub controller program 300 isprogrammed to perform scrubbing operations locally or remotely vianetwork 140. The operation of scrub controller program 300 is describedin further detail with respect to FIG. 3.

FIG. 2 is a block diagram illustrating distributed data processingenvironment 200. Distributed data processing environment 200 illustratesmemory 112 of computer server 110 within distributed data processingenvironment 100 of FIG. 1, in accordance with an embodiment of thepresent invention. In this example, main memory channel 114 (FIG. 1) isequally divided by scrub controller program 300 into main memory channelfirst half 210 and main memory channel second half 212. Similarly,mirrored memory channel 116 is equally divided by scrub controllerprogram 300 into mirrored memory channel first half 214 and mirroredmemory channel second half 216. If, for example, a scrubbing addressrange of a memory channel is represented as ranging from 0 to N, theaddress range of main memory channel first half 210 would consist ofhalf the total address range of main memory, or 0 to N/2, of the totaladdress range of main memory channel 114 from 0 to N. Main memorychannel second half 212 would consist of the address range of mainmemory channel 114 from (N/2)+1 to N of the total address range of mainmemory channel 114 from 0 to N of a memory channel. In a similar manner,mirrored memory channel first half 214 would consist of a first half ofthe total address range of mirrored memory channel 116, or 0 to N/2, andmirrored memory channel second half 216 would consist of the second halfof the total address range of mirrored memory channel 116, or (N/2)+1 toN. It should be noted that although equal division of memory channelsmay offer a more efficient scrubbing operation, some embodiments of thepresent invention achieve time and power consumption efficiencies fromnon-equal divisions of memory channels.

In this example, scrub controller program 300 scrubs main memory channelfirst half 210, and concurrently scrubs mirrored memory channel secondhalf 216. Scrub rates of the two scrubs may vary, but both memorychannel halves are scrubbed in one full scrub cycle. The process forscrubbing is then repeated at a predetermined or user-initiatedfrequency, for example, every 12 hours. In some embodiments, a fullscrub cycle is one full scrubbing operation of two non-duplicate halvesof mirrored memory address ranges. In that scenario, a full scrubbingoperation of two non-duplicate memory halves is equivalent to a singlepass of an entire memory address range of one memory channel, given thatthe main memory channel address range is a duplicate (with errorexceptions) of the mirrored memory channel address range. In someembodiments of the present invention, scrub controller program 300scrubs main memory channel second half 212 and concurrently scrubsmirrored memory channel first half 214. Scrub rates of the two scrubsmay vary, but both memory channel halves are scrubbed in one full scrubcycle. The process for scrubbing is then repeated at a predetermined oruser-initiated frequency, for example, every 12 hours.

In some embodiments of the present invention, scrub controller program300 operates on an alternated scrub cycle. In a first scrub cycle, scrubcontroller program 300 scrubs main memory channel first half 210 andconcurrently scrubs mirrored memory channel second half 216. Scrub ratesof the two scrubs may vary, but both memory channels are scrubbed in onefull scrub cycle. In a subsequent full scrub cycle, scrub controllerprogram 300 alternates the portions of the main memory channel and themirrored memory channel that are scrubbed. In the alternated full scrubcycle, scrub controller program 300 scrubs main memory channel secondhalf 212, and concurrently, scrubs mirrored memory channel first half214. Scrub rates of the second scrub cycle may vary, but both memorychannel halves are scrubbed in one full scrub cycle. The process ofalternating the memory address ranges of main memory channel 114 andmirrored memory channel 116, for scrubbing operations, is repeated at apredetermined or user-initiated frequency, for example, alternatingmemory channel halves that are scrubbed every 12 hours.

FIG. 3 illustrates operational steps of scrub controller program 300,included within memory controller 130 of computer server 110, withindistributed data processing environment 100 of FIG. 1, in accordancewith an embodiment of the present invention. Scrub controller program300 determines if a mirrored memory system is present within memory 112(step 310). In this example, scrub controller program 300 accesses theaddress ranges of memory 112 (FIG. 1) to determine if memory mirroringis configured. Scrub controller program 300 is applicable to a mirroredmemory system, because duplication of memory channels enables a moreefficient scrubbing operation to be performed.

For the case in which scrub controller program 300 determines that amirrored memory system is present within memory 112 (step 310), scrubcontroller program 300 allocates non-corresponding halves of a mainmemory channel and a mirrored memory channel (step 320). Scrubcontroller program determines a split of the address range of both amain memory channel and mirrored memory channel into two portions. Insome embodiments of the present invention, scrub controller program 300splits the memory address range of both the main memory channel and themirrored memory channel into equal portions. In other embodiments, theportions of split address ranges may not be equal; however, thecombination of a portion of the main memory channel and anon-overlapping portion of the mirrored memory channel that arescrubbed, covers the equivalent of the entire memory address range of amemory channel of duplicate memory channels.

For example, scrub controller program 300 splits the address range ofmain memory channel 114 (FIG. 2) and mirrored memory channel 116 intotwo equal portions of the respective address ranges, resulting in mainmemory channel first half 210, main memory channel second half 212,mirrored memory channel first half 214, and mirrored memory channelsecond half 216. In some embodiments of the present invention, scrubcontroller program 300 allocates main memory channel first half 210 andmirrored memory channel second half 216 to a scrubbing operation ofmemory controller 130 (step 320). In other embodiments of the presentinvention, scrub controller program 300 allocates main memory channelsecond half 212 and mirrored memory channel first half 214 to thescrubbing operation of memory controller 130.

Subsequent to allocating the appropriate portions of address ranges ofthe main memory channel and the mirrored memory channel to the scrubbingoperation of memory controller 130, scrubbing controller program 300initiates scrubbing operations of the allocated address ranges (step330). Scrubbing operations proceed in which memory controller 130determines and corrects errors using ECC by monitoring bit data readfrom memory 112, identifying bit errors, and replacing bit errors withcorrected bit data in the appropriate location within the memory addressrange.

Having completed a scrubbing cycle of half of the main memory channeladdress range and half of mirrored memory channel address range, scrubcontroller program 300 determines whether the memory channel halves tobe scrubbed are to be alternated in a next scrubbing cycle (decisionstep 340). In this example, scrub controller program determines to scrubthe same halves of the main memory channel address range and themirrored memory channel address range in subsequent scrubbing cycles,(step 340, “NO” branch), and scrub controller program 300 returns tostep 320 for the next subsequent scrubbing cycle and proceeds asdescribed above. That is, scrub controller program 300 determines to notalternate memory channel halves after scrubbing main memory channelfirst half 210 (FIG. 2) and mirrored memory channel second half 216. Inthe next scrubbing cycle, scrub controller program 300 again scrubs mainmemory channel first half 210 and mirrored memory channel second half216 as described above beginning with step 320.

In some embodiments of the present invention where scrub controllerprogram 300 operates on an alternated full scrub cycle, scrub controllerprogram 300 determines to alternate between the halves of the mainmemory channel address range and the mirrored memory channel addressrange in the next scrubbing cycle (step 340, “YES” branch). In the nextscrubbing cycle, scrub controller program 300 allocates alternatenon-corresponding halves of the main memory channel and the mirroredmemory channel to the memory controller to perform the next memory scruboperation (step 350). Scrub controller program 300 scrubs the halves ofthe memory channel address ranges that were not scrubbed in the previousscrubbing cycle by allocating the alternate main memory channel half andalternate mirrored memory channel half to a scrubbing operation ofmemory controller 130. For example, scrub controller program 300determines to alternate memory channel halves after scrubbing mainmemory channel first half 210 (FIG. 2) and mirrored memory channelsecond half 216 in the first scrubbing cycle. In the second scrubbingcycle, scrub controller program 300 allocates main memory channel secondhalf 212 and mirrored memory channel first half 214 for the scrubbingoperation (step 350).

Subsequent to allocating the appropriate memory address ranges of mainmemory channel second half 212 and mirrored memory channel first half214 to the scrubbing operation of memory controller 130, scrubcontroller program 300 initiates scrubbing operations of the allocatedaddress ranges (step 360). Scrubbing operations proceed in which memorycontroller 130 determines and corrects errors using ECC by monitoringbit data read from memory 112, identifying bit errors, and replacing biterrors with corrected bit data in the appropriate location within theaddress range.

In response to completion of the current instance of a full scrubbingcycle, the current instance of scrubbing of main memory channel secondhalf 212 and mirrored memory channel first half 214 terminates, scrubcontroller program 300 determines whether to repeat an alternation ofmemory channel halves for the next cycle (decision step 370). In thisexample, scrub controller program determines to alternate memory channelhalves for the next cycle, (step 370, “YES” branch), and scrubcontroller program 300 returns to decision step 340 and determineswhether to alternate between the halves of the main memory channel andmirrored memory channel for the next subsequent scrubbing cycle, andproceeds as described above.

In some embodiments of the present invention, scrub controller program300 determines to not alternate the halves of the main memory channeladdress range and the mirrored memory channel address range for the nextscrubbing cycle and scrub controller program 300 ends (step 370, “NO”branch). In the next scrubbing cycle, scrub controller program 300allocates the non-corresponding halves of the main memory channel andthe mirrored memory channel to the memory controller to perform the nextmemory scrub operation when the program begins again.

FIG. 4 illustrates flowchart 400 which shows additional operationalsteps of scrub controller program 300, included within memory controller130 of computer server 110, within distributed data processingenvironment 100 of FIG. 1, in accordance with an embodiment of thepresent invention. Scrub controller program 300 allocatesnon-corresponding halves of a main memory channel and a mirrored memorychannel (step 410) as described in FIG. 3.

Subsequent to allocating the appropriate portions of address ranges ofthe main memory channel and the mirrored memory channel to the scrubbingoperation of memory controller 130, scrubbing controller program 300initiates scrubbing operations of the allocated address ranges (step420) as also described in FIG. 3.

Having completed a scrubbing cycle of half of the main memory channeladdress range and half of mirrored memory channel address range, scrubcontroller program 300 determines whether the allocated memory addressranges are completely scrubbed (step 430). In this example, scrubcontroller program 300 does not proceed until all allocated memoryaddress ranges are scrubbed in one scrub cycle. Scrub controller program300 waits until the allocated memory address ranges are scrubbed beforeproceeding.

FIG. 5 depicts a block diagram of components of computing system 500,which includes computing device 505, which is capable of operating scrubcontroller program 300 of FIG. 3, in accordance with an embodiment ofthe present invention. It should be appreciated that FIG. 5 providesonly an illustration of one implementation and does not imply anylimitations with regard to the environments in which differentembodiments may be implemented. Many modifications to the depictedenvironment may be made.

Computing device 505, includes components and functional capabilitysimilar to computer server 110 and computer server 120, in accordancewith an illustrative embodiment of the present invention. Computingdevice 505 includes communications fabric 502, which providescommunications between computer processor(s) 504, memory 506, persistentstorage 508, communications unit 510, and input/output (I/O)interface(s) 512. Communications fabric 502 can be implemented with anyarchitecture designed for passing data and/or control informationbetween processors (such as microprocessors, communications and networkprocessors, etc.), system memory, peripheral devices, and any otherhardware components within a system. For example, communications fabric502 can be implemented with one or more buses.

Memory 506, cache memory 516, and persistent storage 508 are computerreadable storage media. In this embodiment, memory 506 includes randomaccess memory (RAM) 514. In general, memory 506 can include any suitablevolatile or non-volatile computer readable storage media.

In some embodiments of the present invention, scrub controller program300 is stored in persistent storage 508 for execution by one or more ofthe respective computer processor(s) 504 via one or more memories ofmemory 506. In these embodiments, persistent storage 508 includes amagnetic hard disk drive. Alternatively, or in addition to a magnetichard disk drive, persistent storage 508 can include a solid state harddrive, a semiconductor storage device, read-only memory (ROM), erasableprogrammable read-only memory (EPROM), flash memory, or any othercomputer readable storage media that is capable of storing programinstructions or digital information.

The media used by persistent storage 508 may also be removable. Forexample, a removable hard drive may be used for persistent storage 508.Other examples include optical and magnetic disks, thumb drives, andsmart cards that are inserted into a drive for transfer onto anothercomputer readable storage medium that is also part of persistent storage508.

Communications unit 510, in these examples, provides for communicationswith other data processing systems or devices, including resources ofdistributed data processing environment 100 and computer servers 110 and120. In these examples, communications unit 510 includes one or morenetwork interface cards. Communications unit 510 may providecommunications through the use of either or both physical and wirelesscommunications links. Scrub controller program 300 may be downloaded topersistent storage 508 through communications unit 510.

I/O interface(s) 512 allows for input and output of data with otherdevices that may be connected to computing system 500. For example, I/Ointerface 512 may provide a connection to external devices 518 such as akeyboard, keypad, a touch screen, and/or some other suitable inputdevice. External devices 518 can also include portable computer readablestorage media such as, for example, thumb drives, portable optical ormagnetic disks, and memory cards. Software and data used to practiceembodiments of the present invention, e.g., scrub controller program 300can be stored on such portable computer readable storage media and canbe loaded onto persistent storage 508 via I/O interface(s) 512. I/Ointerface(s) 512 also connect to a display 520.

Display 520 provides a mechanism to display data to a user and may be,for example, a computer monitor.

The programs described herein are identified based upon the applicationfor which they are implemented in a specific embodiment of theinvention. However, it should be appreciated that any particular programnomenclature herein is used merely for convenience, and thus theinvention should not be limited to use solely in any specificapplication identified and/or implied by such nomenclature.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A computer-implemented method of scrubbing acomputer memory of a computing device in a mirrored memory system, thecomputer-implemented method comprising: allocating a main memorypartition of a mirrored memory system and a mirrored memory partition ofthe mirrored memory system for scrubbing, the mirrored memory partitionbeing a mirrored copy of the main memory partition, dividing the mainmemory partition into a first main memory portion and a second mainmemory portion; dividing the mirrored memory partition into a firstmirrored memory portion and a second mirrored memory portion;determining a full scrub cycle that only scrubs a portion of the mainmemory partition and a portion of the mirrored memory partition, thefull scrub cycle including scrubbing a main memory scrub portion and amirrored memory scrub portion, the main memory scrub portion being oneof the first and the second main memory portions and the mirrored memoryscrub portion being one of the first and the second mirrored memoryportions; and initiating the full scrub cycle; wherein: the full scrubcycle includes a combination of memory portions, the combination beingequivalent to a memory address range of the main memory partition. 2.The method of claim 1, further comprising: determining the main memoryscrub portion of the main memory partition and the mirrored memory scrubportion of the mirrored memory partition scrubbed during performance ofa most recent scrubbing of the computer memory of the computing device;determining an expiration of a predetermined period of time sincecompletion of the most recent scrubbing of the computer memory of thecomputing device; and initiating a consecutive scrubbing of the computermemory of the computing device, wherein the main memory scrub portion ofthe main memory partition and the mirrored memory scrub portion of themirrored memory partition that are scrubbed is alternated from the mainmemory scrub portion of the main memory partition and the mirroredmemory scrub portion of the mirrored memory partition scrubbed duringthe most recent previous scrubbing of the memory of the computingdevice.
 3. The method of claim 1, wherein the main memory scrub portionof the main memory partition includes one half of the computer memory ofthe main memory partition and the mirrored memory scrub portion of themirrored memory partition includes one half of the computer memory ofthe mirrored memory partition, wherein content of the main memory scrubportion of the main memory partition, and content of the mirrored memorypartition of the mirrored memory partition, are distinct.
 4. The methodof claim 1, wherein allocating the main memory partition and themirrored memory partition is performed on a network connected to aremote computing device.
 5. The method of claim 1, wherein the mainmemory scrub portion of the main memory partition and the mirroredmemory scrub portion of the mirrored memory partition includenon-consecutive portions of respective memory partitions.
 6. The methodof claim 1, wherein the memory address range of the computing deviceincludes more than two partitions of memory, and the combination of atleast one portion of all partitions of memory is equivalent to onecomplete partition of memory, and each of the more than two partitionsof memory is a duplicate.
 7. The method of claim 6, wherein thecomputing device includes a redundant array of independent disks (RAID).8. The method of claim 1, wherein the computer memory of the computingdevice utilizes the mirrored memory system, wherein the mirrored memorysystem includes the main memory partition and the mirrored memorypartition that in combination defines the memory address range of thecomputing device, and wherein the mirrored memory partition is a copy ofthe main memory partition.
 9. A computer program product for scrubbing acomputer memory of a computing device in a mirrored memory system, thecomputer program product comprising: one or more computer-readablestorage media, and program instructions stored on the one or morecomputer-readable storage media, executable by one or more processors,the stored program instructions comprising: program instructions toallocate a main memory partition of a mirrored memory system and amirrored memory partition of the mirrored memory system for scrubbing,the mirrored memory partition being a mirrored copy of the main memorypartition, program instructions to divide the main memory partition intoa first main memory portion and a second main memory portion; programinstructions to divide the mirrored memory partition into a firstmirrored memory portion and a second mirrored memory portion; programinstructions to determine a full scrub cycle that only scrubs a portionof the main memory partition and a portion of the mirrored memorypartition, the full scrub cycle including scrubbing a main memory scrubportion and a mirrored memory scrub portion, the main memory scrubportion being one of the first and the second main memory portions andthe mirrored memory scrub portion being one of the first and the secondmirrored memory portions; and program instructions to initiate the fullscrub cycle; wherein: the full scrub cycle includes a combination ofmemory portions, the combination being equivalent to a memory addressrange of the main memory partition.
 10. The computer program product ofclaim 9, the stored program instructions further comprising: programinstructions to determine the main memory scrub portion of the mainmemory partition and the mirrored memory scrub portion of the mirroredmemory partition scrubbed during performance of a most recent scrubbingof the computer memory of the computing device; program instructions todetermine an expiration of a predetermined period of time sincecompletion of the most recent scrubbing of the computer memory of thecomputing device; and program instructions to initiate a consecutivescrubbing of the computer memory of the computing device, wherein themain memory scrub portion of the main memory partition and the mirroredmemory scrub portion of the mirrored memory partition that are scrubbedis alternated from the main memory scrub portion of the main memorypartition and the mirrored memory scrub portion of the mirrored memorypartition scrubbed during the most recent previous scrubbing of thememory of the computing device.
 11. The computer program product ofclaim 9, wherein the main memory scrub portion of the main memorypartition includes one half of the computer memory of the main memorypartition and the mirrored memory scrub portion of the mirrored memorypartition includes one half of the computer memory of the mirroredmemory partition, wherein content of the main memory scrub portion ofthe main memory partition, and content of the mirrored memory partitionof the mirrored memory partition, are distinct.
 12. The computer programproduct of claim 9, wherein allocating the main memory partition and themirrored memory partition is performed on a network connected to aremote computing device.
 13. The computer program product of claim 9,wherein the main memory scrub portion of the main memory partition andthe mirrored memory scrub portion of the mirrored memory partitioninclude non-consecutive portions of respective memory partitions. 14.The computer program product of claim 9, wherein the memory addressrange of the computing device includes more than two partitions ofmemory, and the combination of at least one portion of all partitions ofmemory is equivalent to one complete partition of memory, and each ofthe more than two partitions of memory is a duplicate.
 15. The computerprogram product of claim 14, wherein the computing device includes aredundant array of independent disks (RAID).
 16. The computer programproduct of claim 9, wherein the computer memory of the computing deviceutilizes the mirrored memory system, wherein the mirrored memory systemincludes the main memory partition and the mirrored memory partitionthat in combination defines the memory address range of the computingdevice, and wherein the mirrored memory partition is a copy of the mainmemory partition.
 17. A computer system for scrubbing a computer memoryof a computing device in a mirrored memory system, the computer systemcomprising: one or more computer processors; one or more computerreadable storage device; program instructions stored on the one or morecomputer readable storage devices for execution by at least one of theone or more computer processors, the stored program instructionscomprising: program instructions to allocate a main memory partition ofa mirrored memory system and a mirrored memory partition of the mirroredmemory system for scrubbing, the mirrored memory partition being amirrored copy of the main memory partition, program instructions todivide the main memory partition into a first main memory portion and asecond main memory portion; program instructions to divide the mirroredmemory partition into a first mirrored memory portion and a secondmirrored memory portion; program instructions to determine a full scrubcycle that only scrubs a portion of the main memory partition and aportion of the mirrored memory partition, the full scrub cycle includingscrubbing a main memory scrub portion and a mirrored memory scrubportion, the main memory scrub portion being one of the first and thesecond main memory portions and the mirrored memory scrub portion beingone of the first and the second mirrored memory portions; and programinstructions to initiate the full scrub cycle; wherein: the full scrubcycle includes a combination of memory portions, the combination beingequivalent to a memory address range of the main memory partition. 18.The computer system of claim 17, the stored program instructions furthercomprising: program instructions to determine the main memory scrubportion of the main memory partition and the mirrored memory scrubportion of the mirrored memory partition scrubbed during performance ofa most recent scrubbing of the computer memory of the computing device;program instructions to determine an expiration of a predeterminedperiod of time since completion of the most recent scrubbing of thecomputer memory of the computing device; and program instructions toinitiate a consecutive scrubbing of the computer memory of the computingdevice, wherein the main memory scrub portion of the main memorypartition and the mirrored memory scrub portion of the mirrored memorypartition that are scrubbed is alternated from the main memory scrubportion of the main memory partition and the mirrored memory scrubportion of the mirrored memory partition scrubbed during the most recentprevious scrubbing of the memory of the computing device.
 19. Thecomputer system of claim 17, wherein the main memory scrub portion ofthe main memory partition includes one half of the computer memory ofthe main memory partition and the mirrored memory scrub portion of themirrored memory partition includes one half of the computer memory ofthe mirrored memory partition, wherein content of the main memory scrubportion of the main memory partition, and content of the mirrored memorypartition of the mirrored memory partition, are distinct.
 20. Thecomputer system of claim 17, wherein allocating the main memorypartition and the mirrored memory partition is performed on a networkconnected to a remote computing device.